Copolymers of trifluorochloroethylene



United States Patent COPOLYMERS OF TRIFLUOROCHLORO- ETHYLENE Francis J. Honn, Westfield, N.J., and John M. Hoyt, Woodside, N.Y., assignors, by mesne assignments, to Minnesota Mining and Manufacturing Company, St. Paul, Mium, a corporation of Delaware No Drawing. Application June 25, 1956 Serial No. 593,383

Claims. (Cl. 26087.'5)

This invention relates to, and has for its object, the preparation of new and useful copolymers of trifluorochloroethylene. More particularly, the invention relates to, and has for its object, the preparation of thermoplastic copolymers of trifluorochloroethylene having a wide variety of commercial uses and applications. Still more particularly, the invention relates to, and has for its object, a method for the preparation 'of these copolymers. Other objects and advantages inherent in the invention will become apparent to those skilled in the art from the accompanying description'and disclosure.

In accordance with the present invention, trifluorochloroethylene is copolymerized with a hexafluorobutene, for example, 2,3-dichlorohexafluorobutene2 or l,1,1,4, 4,4-hexafluorobutene-2 to produce new and useful copolymeric compositions. In this respect, it is found that these copolymeric compositions possess increased resistance to oil and hydrocarbon fuels, improved flow-properties, and improved chemical and physical stability over any of the aforementioned comonomers alone. These copolymeric compositions of trifiuorochloroethylene and the aforementioned hexafluorobutenes, constitute valuable macromolecules and are adaptable to a wide variety of commercial uses. They are particularly valuable, because of their selective solubility in various commercial solvents, in serving as durable, flexible, protective coatings on surfaces which are subjected to environmental conditions in which they may come into contact with any of the aforementioned corrosive substances.

In general, as more fully hereinafter disclosed, the

copolymeric compositions of the present invention are produced from monomeric mixtures containing trifluorochloroethylene and the hexafluorobutene, as a comonomer, at temperatures between about 20 C. and about 150 C., with intermediate temperature ranges being selected with reference to the specific copolymer system employed. The most useful thermoplastic copolymeric compositions of the present invention are copolymers produced from monomeric mixtures containing between about 10 mole percent and about 90 mole percent of the trifluorochloroethylene and the remaining major constituent being the hexafiuorobutene. The preferred copolymeric compositions of the present invention are copolymers produced from monomeric mixtures containing between about 25 mole percent and about 75 mole percent of the trifluorochloroethylene and the remaining major constituent being the hexafluorobutene. As previously indicated, preferred examples of the hexafluorobutene co monomer, copolymerized with the trifluorochloroethylene, are 2,3-dichlorohexafiuorobutene-Z or 1,1,l,4,4,4-hexafluorobutene-Z.

The polymeric compositions of the present invention are preferably prepared by carrying out the polymerization reaction in the presence of a free-radical-forming promoter. For this purpose, the polymerization reaction is carried out by employing a water-soluble peroxy type initiator in a wa ter-s uspens ion ,typerecipe oran organic V v peroxide initiator in a bulk-type system. The watersuspension type recipe is preferred.

The water-suspension type system contains a watersoluble peroxy-type initiator, which is preferably present in the form of an inorganic persulfate such as potassium persulfate, sodium persulfate or ammonium persulfate. In addition, the water-suspension type recipe system may also contain, in some instances, a variable-valence metal salt, for example, an iron salt such as ferrous sulfate or ferrous nitrate to accelerate the copolymerization reaction. The water-soluble initiator present in the water-suspension type recipe system comprises between about 0.1 and about 5 parts by weight per parts of total monomers present. The variable-valence metal salt is preferably employed in an amount between about 0.01 and about 0.2

part by weight per 100 parts of total monomers present.

It is also desirable, in some instances, in these watersuspension type recipe systems, that a reductant be present, preferably in the form of a bisulfite, such as sodium bisulfite, potassium bisulfite, sodium metabisulfite or potassium metabisulfite. The reductant comprises between about 0.05 and about 5 parts by weight per 100 parts of total monomers present; preferably the reductant comprises between about 0.1 and about 2 parts by weight per 100 parts of total monomers present.

In these water-suspension type recipe systems, it is deenable to employ an emulsifying agent. This emulsifying agent is present either in the form of a metallic salt of an aliphatic acid having from 14 to 20 carbon atoms per molecule, or in the form of a halogenated-organic acid or salts thereof, having from 6 to 18 carbon atoms per molecule. A typical example of the former is potassium stearate. Typical examples of the halogenated-organic acid or salts thereof, serving as emulsifying agents in the above-mentioned water-suspension type recipe systems, are polyfiuorocarboxylic acids (e.g., perfluorooctanoic acid) or perfiuorochlorocarboxylic acid salts (e.g., trifluorochloroethylene telomer acid soaps). The polyfiuorocarboxylic acids which may be employed are such as those disclosed in US. Patent No. 2,559,752; and the non-acidic derivatives of the acids disclosed therein as being effective dispersing agents may also be used in the process of the present invention. The perfluorochlorocarboxylic acid salts which may be used in accordance with this invention are those disclosed in co-pending application Serial No. 501,782, filed April 18, 1955, as being useful dispersing agents in polymerization reactions. In general, these emulsifying agents are present in an amount between about 0.5 and about 10 parts by weight per 100 parts of total monomers present.

The polymerization reaction is preferably conducted under alkaline conditions. It is desirable, therefore, that the pH be maintained between about 7 and 11 in order to prevent gelling of the resulting polymeric product, a condition which often causes slowdown or stoppage of the polymerization reaction. In this respect, it should be noted that it is sometimes necessary to maintain the pH of the system within the aforementioned pH limits by the addition of suitable butter agents. Typical examples are sodium borate and disodium phosphate.

As indicated above, the polymerization reaction may also be carried out with the initiater being present in the form of an organic peroxide in a bulk-type polymerization system. Of these organic peroxide promoters, halogen-substituted peroxides are most desirable. A preferred promoter of this type is trichloroacetyl peroxide. Other halogen-substituted organic peroxides for carrying out the polymerization reaction are trifluorodichloropropionyl peroxide, trifiuoroacetyl peroxide, difiuoroacetyl peroxide, trichlor oacetyl peroxide, 2,4 -dichloro-,

benzoyl peroxide and dichlorofluoroacetyl peroxide, benzoyl peroxide and di-tertiary butyl peroxide.

As previously indicated, the polymerization reaction is carried out, in general, at a temperature between-about 20 C. and about 150 C. When the polymerization re; action is carried out employing a water-suspension type recipe, temperatures between about C. and about 100 C. are preferably employed. When the polymerization reaction is carried out in the presence of an organic peroxide initiator in a bulk-type polymerization system, temperatures over the entire range of between about 20 C. and about 150 C. are preferably employed depending upon the decomposition temperature of the promoter. The polymerization reactions described herein to produce the polymeric compositions of the present invention are carried out under autogenous conditions of pressure.

As previously indicated,'the polymerization compositions of the present invention are particularly suitable and useful when employed in the form of durable, flexible coatings on'a wide variety of surfaces, and particularly on surfaces wh ch are subjected to distortion in normal use, such as fabric surfaces. For this purpose, the polymeric composition may be dissolved in various commercial solvents. Particularly useful solvents comprise the aliphatic andaromatic esters, ketones and halogenated hydrocarbons. Typical examples of these solvents are di-isobutyl ketone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate and 1,1,2-trifluorotrichloroethane. In this respect, it should be noted that it is often desirable to regulatethe-molecular weight of the polymeric compositions of the present invention in order to obtain greater solubility in organic solvents. It is found-that the'addition of various polymerization modifiers appreciably reduces the molecular weight ofthe polymeric compositions and increases their solubility, without affecting, unduly, the :overall yield. Suitable polymerization modifiers include chloroform (CHClg), Freon-113 (CF ClCFCl carbon tetrachloride (CCl trichloroacetyl chlorine (CCl COCl), bromotrichlorometane (CBrCl dodecyl mercaptan (C H SH) and mixed tertiary mercaptans. These modifiers are preferably added in amounts between about 0.01 and about parts by weight per 100 parts of total monomers charged to the polymerization reaction. Chloroform is preferred.

The following examples are offered for a better understanding in producing the copolymeric compositions of the present invention and are not to .be construed as limiting its scope.

Example I A heavy-walled glass polymerization tube of about 300 ml. capacity wasfiushed with nitrogen and then charged with ml. of a catalyst solution prepared by dissolving 2.5 grams of potassium persulfate in 100 ml. of water. This solution -in the polymerization tube was then frozen. Thereafter, there was added to the polymerization tube 10 ml.'of a solution prepared by dissolving 2 grams of sodium metabisulfate in 100 ml. of water. The contents of the tube were then refrozen. Thereafter,tl1ere wereadded to the frozen contents of the tube 10 ml. of a solution prepared by dissolving 0.5 gram of ferrous sulfate heptahydrate in 100 ml. of water. The contents of the tube were once more frozen. The tube was next connected to a gas-transfer system and evacuated at liquid nitrogen temperature. To the frozen contents of the tube were. added, by distillation, 16 grams of trifluorochloroethylene and 33.4 grams of 2,3-dichlorohexafluorobutenelZ, which comprised a 50/50 molar ratio.

The 2,3-dichlorohexafiuorobutene-Z is prepared according to the procedure described by Henne and Trott, Journal of the American Society, volume 69, page 1820 947).

The polymerization tube was next sealed under vacuum and agitated in a temperature-regulated water-bath at 20 C. for a period of 64 hours. At the end of this time, the contents of the tube were coagulated by freezing at liquid nitrogen temperature. The coagulated product was then removed from the tube, washed with hot water and then dried to constant weight in vacuo at 35 C. A thermoplastic copolymeric product was obtained which was found to comprise trifluorochloroethylene and 2,3-diclilorohexafluorobutene-Z in an amount of 4.5 grams. This amount corresponded to a 9% conversion.

Example If Employing the procedure set forth in Example I and the same polymerization system, the tube was charged "with 31.2 grams of trifluorochloroethylene and. 18.8 grams of 2,3-dichlorohexafiuorobutene2, which comprised a 77/23 molar ratio. The polymerization reaction was carried out at a temperature of 20 C. for a period of.64 hours. The resultant product was workedup in accordance with the same procedure as set forth in Example I. A thermoplasticcopolymeric product was obtained which was found to comprise trifluorochloroethylene and 2,3-dichlorohexafiuorobutene-2 in an amount of 21 grams. This amount corresponded to a 42% conversion.

Example III Employing the procedure set forth in Example I, the same catalyst system was employed, except that ammonium persulfate was substituted for the potassium persulfate, in a similar amount of 2.5 grams. The polymerization tube was next charged with 20.8 grams of trifluorochloroethylene and 29.2 grams of cis-1,1,1,4,4,4- hexafluorobutene-Z, which comprised a 50/50 molar ratio. The cis-l,l,1,4,4,4-hexafluorobutene-2 is prepared according to theprocedure described by A. L. Henne and W. G. Finnegan, Journal of the American Chemical Society, volume 71, page 298 (1949).

The polymerization reaction was carried out at a temperature of 20 C. for a period of 23 hours. The resultant product was worked-up in accordance with the same procedure as set forth in Example I. A thermoplastic copolymeric product was obtained which was found to comprise trifluorochloroethylene and cis-l,l,l, 4,4,4-hexafiuorobutene-2 in an amount of 2 grams. This amount corresponded to a 4% conversion.

Aspreviously indicated, the polymeric compositions of the present invention possess highly desirable physical and chemical properties which make them useful for application to various surfaces as protective coatings. Whenemployed as protective coatings on any of the surfaces previously described, the raw copolymeric composition, such as is produced in accordance with the procedure set forth in the above examples, is dissolved in anyofthe aforementioned solvents and is applied to the desired surfaces, employing such apparatus as a knifespreader or a doctor-blade or-a reverse-roll coater. The solvent, after the copolymeric coating composition has been applied to the surface, is permitted to evaporate. This may also be accomplished in the presence of elevated temperatures, if so desired. In many applications, it is desirable to include in the copolymeric coating composition, vvarious vulcanizing agents. In the latter case, supplementary heat-treatment of the coating is required, either during the solvent-removal step or thereafter. After the solventhas been completely evaporated, the coated surface is ready for use. In this respect, it should be noted that the polymeric coating composition may be applied to the surface either as a single coating or, if so desired, the protective coatingmay be built-up by the application of several layers, each layer being permitted to harden by solventevaporation before the next layer is applied. Furthermore, if so desired, the protective coatings, or the polymeric composition, when obtained in the form of sheets, may be "suitably pigmented.

Other uses for the copolymeric compositions of the present invention reside as coatings in the fabrication of pressure-sensitive tape for electrical insulation purposes,

or as adhesives for fastening a rubber surface to a metal or another rubber surface.

Since certain changes may be made in carrying out the process of the present invention in producing the desired polymeric compositions without departing from the scope of the invention, it is intended that all matter contained in the above description is to be interpreted as illustrative and not in a limiting sense.

We claim:

1. A process which comprises polymerizing a monomeric mixture of trifiuorochloroethylene and a hexafiuorobutene selected from the group consisting of 2,3- dichlorohexafluorobutene- 2 and 1,1,1,4,4,4-hexafiuorobutene-Z, said mixture containing between about mole percent and about 90 mole percent trifluorochloroethylene and the remaining major constituent being the hexafluorobutene, in the presence of a free-radical-forming polymerization promoter at a temperature between about C. and about 150 C.

2. A process which comprises polymerizing a monomeric mixture consisting essentially of trifluorochloroethylene and a hexafluorobutene selected from the group consisting of 2,3-dichlorohexafiuorobutene-2 and 1,1,1, 4,4,4-hexafluorobutene-2, said mixture containing between about mole percent and about 75 mole percent trifiuorochloroethylene in the presence of a free-radicalforming polymerization promoter at a temperature between about 20 C. and about 150 C.

3. A process which comprises polymerizing a mono meric mixture consisting essentially of trifluorochloroethylene and 2,3-dichlorohexafluorobutene-Z, said mixture containing between about 10 mole percent and about 90 mole percent trifluorochloroethylene in the presence of a free-radical-forming polymerization promoter at a temperature between about 20 C. and about 150 C.

4. A process which comprises polymerizing a monomeric mixture consisting essentially of trifluorochloroethylene and 1,1,1,4,4,4-hexafluorobutene-2, said mixture containing between about 10 mole percent and about 90 mole percent trifluorochloroethylene, in the presence of a free-radical-forming polymerization promoter at a temperature between about -20 C. and about 150 C.

5. A process which comprises polymerizing a monomeric mixture consisting essentially of trifluorochloxoethylene and 2,3-dichlorohexafiuorobutene-2, said mixture containing between about 25 mole percent and about mole percent trifluorochloroethylene, in the presence of a free-radical-forming polymerization promoter at a temperature between about 20 C. and about 150 C.

6. A process which comprises polymerizing a monomeric mixture consisting essentially of trifluorochloroethylene and 1,1,1,4,4,4-hexafluorobutene-2, said mixture containing between about 25 mole percent and about 75 mole percent trifluorochloroethylene, in the presence of a free-radical-forming polymerization promoter at a temperature between about -20 C. and about 150 C.

7. A copolymer consisting essentially of monomer units corresponding to trifluorochloroethylene and a hexafluorobutene selected from the group consisting of 2,3- dichlorohexafluorobutene-2 and 1,1,1,4,4,4-hexafluorobutene-2 containing between about 10 mole percent and about mole percent of trifluorochloroethylene.

8. A copolymer consisting essentially of monomer units corresponding to trifluorochloroethylene and 2,3- dichlorohexafluorobutene-2 containing between about 25 mole percent and about 75 mole percent of trifluorochloroethylene.

9. A copolymer consisting essentially of monomer units corresponding to trifiuorochloroethylene and 1,1,1, 4,4,4-hexafiuorobutene-2 containing between about 25 mole percent and about 75 mole percent of trifiuorochloroethylene.

10. A process which comprises polymerizing a watersuspension system a monomeric mixture consisting essentially of trifiuorochloroethylene and a hexafluorobutene selected from the group consisting of 2,3-dichlorohexafluorobutene-Z and 1,1,1,4,4,4-hexafluorobutene-2, said mixture containing between about 10 mole percent and about 90 mole percent trifiuorochloroethylene, in the presence of a free-radical-forming polymerization promoter at a pH of between about 7 and 11 at a temperature between about 5 C. and about C.

References Cited in the file of this patent UNITED STATES PATENTS 2,684,959 Rearick July 27, 1954 2,705,706 Dittman et al. Apr. 5, 1955 2,774,109 Kaufman Dec. 18, 1956 2,774,751 Passino et al. Dec. 18, 1956 Attesting @flicer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent Non 2,915,509 December 1, 1959 Francis JD norm et ale It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Oolunm 3, line 40, for "chlorine" read. m chloride line 41 for "metane" read methane line 60, for "metabisulfate" read Lee metabisulfite same column 3 line '70, for chlorohexafluorobutene-l?)," read me chlorohexafluorobutene Signed and sealed this 10th day of May 1960.,

(SEAL) Attest:

KARL Ha AXLINE ROBERT C. ATSON Commissioner of Patents 

1. A PROCESS WHICH COMPRISES POLYMERIZING A MONOMERIC MIXTURE OF TRIFLUOROCHLOROETHYLENE AND A HEXAFLUOROBUTENE SELECTED FROM THE GROUP CONSISTING OF 2,3DICHLOROHEXAFLUOROBUTENE- 2 AND 1,1,1,4,4,4-HEXAFLUOROBUTENE-2, SAID MIXTURE CONTAINING BETWEEN ABOUT 10 MOLE PERCENT AND ABOUT 90 MOLE PERCENT TRIFLUOROCHLOROETHYLENE AND THE REMAINING MAJOR CONSTITUENT BEING THE HEXAFLUOROBUTENE, IN THE PRESENCE OF A FREE-RADICAL-FORMING POLYMERIZATION PROMOTER AT A TEMPERATURE BETWEEN ABOUT-20* C. AND ABOUT 150* C. 